package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    StringRedisTemplate stringRedisTemplate;

    @Resource
    CacheClient cacheClient;

    /**
     * 把商铺存入redis中,用缓存空值的方法解决缓存穿透问题
     * @param id
     * @return
     */
    @Override
    public Result queryById(Long id) {

        //缓存穿透
        //Shop shop = queryWithPassThrough(id);

        //用封装后的代码+解决缓存穿透
        Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id, Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);


        //互斥锁解决缓存击穿
       // Shop shop = queryWithMutex(id);


        //逻辑过期解决缓存穿透
       //Shop shop = queryWithLogicalExpire(id);
        //用封装后的代码+逻辑过期解决缓存穿透
        //Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.SECONDS);


        if (shop == null) {
            return Result.fail("店铺不存在！");
        }

        return Result.ok(shop);
    }

    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否命中未命中 返回空
        if(StrUtil.isBlank(shopJson)){
            //3.不存在，直接返回
            return null;
        }
        //4.命中，需要json反序列化对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);

        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);

        LocalDateTime expireTime = redisData.getExpireTime();

        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {

            //5.1 未过期直接返回店铺信息
            return shop;
        }
        //5.2已过期 需要缓存重建

        //6.缓存重建
        //6.1获取互斥锁
        //6.2判断是否获取锁成功

        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);

        //6.3成功 开启独立线程实现缓存重建
        if (isLock){

            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    this.saveShop2Redis(id,20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unLock(lockKey);
                }
            });
        }

        //6.4返回过期的商铺信息

        return shop;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public Shop queryWithMutex(Long id){

        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在这里是判断是否 是null值和"" 如果是 则输出false
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是("") 上面已经判断是否为空了
        // 如果不为空则执行这一句,
        //如果这里是""会执行此句
        if (shopJson != null) {

            return null;
        }

        //4.实现缓存重建
        //4.1获取互斥锁

        String lockKey = "lock:shop:" + id;
        Shop shop = null;

        try {
            boolean isLock = tryLock(lockKey);

            //4.2判断是否获取成功
            //4.3失败，则休眠重试
            if (!isLock){
                Thread.sleep(50);
                return   queryWithMutex(id);
            }
            //4.4成功 根据id查询数据库
            shop = getById(id);

            //模拟重建延时
            Thread.sleep(200);

            //5.不存在，返回错误
            if (shop == null){

                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);

                return null;
            }

            //6.存在，写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        finally {
            //7.释放互斥锁
            unLock(lockKey);
        }

        return shop;
    }

    /**
     * 这里用缓存空字符串的方法解决缓存穿透问题
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在这里是判断是否 是null值和"" 如果是 则输出false
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是("") 上面已经判断是否为空了
        // 如果不为空则执行这一句,
        //如果这里是""会执行此句 此处的空值来自当数据库为空值时缓存的
        if (shopJson != null) {

            return null;
        }

        //4.不存在，根据id查询数据库
        Shop shop = getById(id);

        //5.不存在，返回错误
        if (shop == null){

            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);

            return null;
        }

        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        return shop;
    }

    /**
     * 获得锁
     * @param key
     * @return
     */
    private boolean tryLock(String key){

        //利用setnx命令来设置锁，此命令不能修改已经存在的key
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);

        //不能直接写拆箱，因为有可能出现空指针 用hutool工具把Boolean 转化为boolean
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 释放锁
     * @param key
     */
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    public void saveShop2Redis(Long id,Long expireSeconds) throws InterruptedException {

        //1.查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);

        RedisData redisData = new RedisData();
        redisData.setData(shop);
        //在现有的时间加上？秒 LocalDateTime.now().plusSeconds(expireSeconds)
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,JSONUtil.toJsonStr(redisData));

    }

    /**
     *缓存更新策略 先写入数据库，然后在删除缓存
     * @param shop
     * @return
     */
    @Override
    @Transactional
    public Result updata(Shop shop) {

        Long id = shop.getId();

        if (id == null) {
            return Result.fail("店铺的id不能为空");
        }


        //1.更新数据库
        updateById(shop);

        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
